@@ -6,6 +6,47 @@ import Basics (Nat)
66-- A sequence of nodes, simple very of graph
77data LinkedList a = Null' | Node' a (LinkedList a ) deriving Show
88
9+ instance Eq a => Eq LinkedList a ) where
10+ Null' == Null' = True
11+ Null' == (Node' _ _) = False
12+ (Node' _ _) == Null' = False
13+ (Node' x1 x2) == (Node' y1 y2) = x1 == y1 && x2 == y2
14+ 15+ testLink = Node' 1 $ Node' 2 $ Node' 1 $ Node' 5 $ Node' 2 $ Node' 3 Null'
16+ 17+ {-
18+ 2.1
19+ Write code to remove duplicates from an unsorted linked list.
20+
21+ Test Case:
22+ removeDup testLink
23+ -}
24+ removeDup :: Eq a => LinkedList a -> LinkedList a
25+ removeDup xs = removeDupHelper xs []
26+ 27+ removeDupHelper :: Eq a => LinkedList a -> [LinkedList a ] -> LinkedList a
28+ removeDupHelper Null' _ = Null'
29+ removeDupHelper (Node' x y) dict
30+ | Node' x Null' `elem` dict = removeDupHelper y dict
31+ | otherwise = Node' x (removeDupHelper y (Node' x Null' : dict))
32+ 33+ -- (no dict)loop into the original list, and refine the result list
34+ removeDupBF :: Eq a => LinkedList a -> LinkedList a
35+ removeDupBF xs = removeDupBFHelper xs xs
36+ 37+ removeDupBFHelper :: Eq a => LinkedList a -> LinkedList a -> LinkedList a
38+ removeDupBFHelper Null' refined = refined
39+ removeDupBFHelper _ Null' = Null'
40+ removeDupBFHelper (Node' x l1) (Node' y l2) =
41+ removeDupBFHelper l1 (refineLink (Node' x Null' ) (Node' y l2) True
42+ 43+ refineLink :: Eq a => LinkedList a -> LinkedList a -> Bool -> LinkedList a
44+ refineLink _ Null' _ = Null'
45+ refineLink x (Node' y l) isFirst
46+ | (x == Node' y Null' ) && not isFirst = refineLink x l isFirst
47+ | (x == Node' y Null' ) && isFirst = Node' y (refineLink x l False
48+ | otherwise = Node' y (refineLink x l isFirst)
49+ 950{-
1051 4.3 Given a binary tree, design an algorithm which creates
1152 a linked list of all the nodes at each depth.
@@ -35,6 +76,6 @@ divideTreeHelper xs track (Just y:ys) =
3576-- Check whether it is belong to the set of power of two
3677isPowerOfTwo :: Nat -> Bool
3778isPowerOfTwo 1 = True
38- isPowerOfTwo x
79+ isPowerOfTwo x
3980 | x `mod` 2 == 1 = False
4081 | otherwise = isPowerOfTwo (x `div` 2 )
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